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Rotating field sensor

a sensor and rotation field technology, applied in the field of rotation field sensors, can solve the problems of difficult sensor design, double the number of wheatstone bridge circuits, and and achieve the effect of reducing the error in the detected angl

Active Publication Date: 2019-08-20
TDK CORPARATION
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention aims to provide a rotating field sensor that can detect an angle with a reduced error. The invention achieves this by generating multiple post-computation signals containing reduced error components of the signal period compared to the first and second signals. The third and fourth signals contain a reduced error component of ¼ of the predetermined signal period, while the fifth and sixth signals contain a reduced error component of ½ of the predetermined signal period. The detected angle value is determined based on these post-computation signals, resulting in a more accurate angle detection.

Problems solved by technology

A distortion of the output signal waveform of each bridge circuit may lead to some error in the angle detected by the rotating field sensor.
This technique, however, requires twice as many Wheatstone bridge circuits as the conventional rotating field sensor which uses two Wheatstone bridge circuits.
This technique, however, requires that the design of the correction sensing elements be optimized according to the design conditions such as the resistances, sizes and materials of the main sensing element and the correction sensing elements and the strength of the rotating magnetic field, and thus has a drawback that the design of the sensor is not easy.
As has been described, a rotating field sensor that uses MR elements as magnetic detection elements has a problem that the angle detected by the rotating field sensor may contain some error.
This problem can occur in any rotating field sensor that includes magnetic detection elements to detect an angle that the direction of a rotating magnetic field forms with respect to a reference direction.

Method used

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first embodiment

[0050]Preferred embodiments of the present invention will now be described in detail with reference to the drawings. First, reference is made to FIG. 1 and FIG. 2 to describe the general configuration of a rotating field sensor according to a first embodiment of the invention. FIG. 1 is a perspective view illustrating the general configuration of the rotating field sensor according to the first embodiment. FIG. 2 is an explanatory diagram illustrating the definitions of directions and angles used in the first embodiment.

[0051]As shown in FIG. 1, the rotating field sensor 1 according to the first embodiment is configured to detect the angle that the direction of a rotating magnetic field MF in a reference position forms with respect to a reference direction. The direction of the rotating magnetic field MF in the reference position rotates when viewed from the rotating field sensor 1. In FIG. 1, a cylindrical magnet 2 is shown as an example of means for generating the rotating magneti...

second embodiment

[0138]A rotating field sensor according to a second embodiment of the invention will now be described with reference to FIG. 10. FIG. 10 is a circuit diagram illustrating the configuration of the rotating field sensor according to the second embodiment. In the second embodiment, the first, second, fifth and sixth directions D1, D2, D5 and D6 are different from those of the first embodiment as described below.

[0139]The first direction D1, which is a direction of the rotating magnetic field MF that maximizes the first signal S1 generated by the first signal generation unit 14A, is the direction rotated clockwise by an angle θ1 greater than 100° and smaller than 140° from the third direction D3 (the −Y direction) of the first embodiment shown in FIG. 2. The fifth direction D5, which is a direction of the rotating magnetic field MF that maximizes the fifth signal S5 generated by the fifth signal generation unit 34A, is the direction rotated counterclockwise by an angle θ2 greater than 1...

third embodiment

[0173]A rotating field sensor according to a third embodiment of the invention will now be described with reference to FIG. 11. FIG. 11 is a circuit diagram illustrating the configuration of the rotating field sensor according to the third embodiment. In the third embodiment, the first to third detection circuits 10, 20 and 30 of the rotating field sensor 1 are configured in the same manner as the first embodiment. The rotating field sensor 1 according to the third embodiment includes an angle detection unit 70 in place of the angle detection unit 60 of the first embodiment. Like the angle detection unit 60, the angle detection unit 70 is configured to generate a detected angle value θs based on the first to sixth signals S1 to S6, the detected angle value θs having a correspondence relationship with the angle θ that the direction DM of the rotating magnetic field MF in the reference position PR forms with respect to the reference direction DR. As shown in FIG. 11, the angle detecti...

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Abstract

A first, a second, and a third computing circuit respectively generate a first post-computation signal with a second harmonic component reduced as compared with first and second signals, a second post-computation signal with the second harmonic component reduced as compared with third and fourth signals, and a third post-computation signal with the second harmonic component reduced as compared with fifth and sixth signals. A fourth and a fifth computing circuit respectively generate a fourth post-computation signal with a third harmonic component reduced as compared with the first and second post-computation signals, and a fifth post-computation signal with the third harmonic component reduced as compared with the second and third post-computation signals. A sixth computing circuit determines a detected angle value based on the fourth and fifth post-computation signals.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a rotating field sensor for detecting an angle that the direction of a rotating magnetic field forms with respect to a reference direction.[0003]2. Description of the Related Art[0004]In recent years, rotating field sensors have been widely used to detect the rotational position of an object in various applications such as detecting the rotational position of an automotive steering wheel. Systems using rotating field sensors are typically provided with means (for example, a magnet) for generating a rotating magnetic field whose direction rotates in response to the rotation of the object. The rotating field sensors use magnetic detection elements to detect the angle that the direction of the rotating magnetic field forms with respect to a reference direction. The rotational position of the object is thus detected.[0005]Among known rotating field sensors is one that includes two bridge cir...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): G01B7/30G01D5/14G01R33/09
CPCG01B7/30G01R33/093G01D5/145
Inventor HIROTA, YOHEITOKIDA, HOMAREHIRABAYASHI, HIRAKU
Owner TDK CORPARATION